1. Field of the Invention
The present invention relates to countermeasures for protecting a vehicle such as an aircraft from a hostile heat-seeking missile, and to methods for effecting countermeasures against a hostile missile.
2. Description of the Related Art
Aircraft, especially military aircraft, often carry pyrotechnic decoy flares as countermeasures for luring incoming anti-aircraft missiles away from the aircraft. A particular type of anti-aircraft missile known as a heat-seeking missile is designed to seek infrared (“IR”) radiation emissions of the aircraft. As a countermeasure to the anti-aircraft missiles, the decoy flares produce heat output designed to attract the anti-aircraft missiles. The decoy flares typically are ejected from the aircraft and remotely or automatically ignited in flight. More sophisticated flares contain a propulsion system for propelling the flare over a flight path similar to, but divergent in direction from, the path of the aircraft. The propulsion system is designed to confuse anti-aircraft missiles that can discriminate between a free-falling flare and a propulsion-powered object, e.g., the aircraft. If the decoy flares function correctly, the anti-aircraft missile will lock into and follow the decoy flare, and cease pursuit of the aircraft, allowing the aircraft to proceed unharmed by the missile.
Conventional decoy flares create infrared radiation by burning a composition of magnesium and polytetrafluoroethylene (TEFLON) powder. This composition produces an emission spectrum that is more intense, but not spectrally identical to that of a jet engine. Aircraft jet engines typically produce longer wavelength infrared emissions than magnesium-TEFLON conventional compositions. Advanced heat-seeking anti-aircraft missiles are able to distinguish between the infrared radiation emissions of an aircraft and the infrared radiation emissions of the magnesium-TEFLON conventional composition.
Even more sophisticated heat-seeking anti-aircraft missiles are able to detect not only for the long wavelength infrared emission signature of exhaust plume of an aircraft, but also the aircraft's metal exhaust port (that is somewhat cooler than the exhaust plume) around the exhaust plume. Such heat-seeking anti-aircraft missiles theoretically will not lock on a countermeasure that does not produce the IR emission signatures of both the exhaust plume and the metal exhaust port.